Inhibition of tumor angiogenesis is a novel approach to cancer treatment that is being actively pursued in clinical trials. Evaluating the efficacy of angiogenesis inhibitors in clinical settings is difficult, because effective therapy may only slow tumor growth and is often indistinguishable from ineffective therapy. Proper evaluation and rational development of these agents may depend on imaging techniques that can report the effects of angiogenesis inhibition in vivo. Optical methods offer the potential to image critical tumor vascular, microenvironmental and metabolic parameters that change with angiogenesis inhibition, and studies in this project will examine, develop and validate these methods in mouse tumor models. Angiogenesis inhibitors target the tumor vascutature, reducing tumor vascularity as their primary effect and inducing or exacerbating tumor ischemia as a derivative effect that slows tumor growth. Aim 1 is to examine and develop the ability of phased-array near-infrared (NIR) optical imaging coupled with use of indocyanine green as a NIR vascular contrast agent to detect changes in tumor vascular volume and perfusion with therapy. This involves the development and validation of reliable and referenced instrumentation and appropriate algorithms for analyzing data. Aim 2 is to examine the ability of oxygen-dependent quenching of the NIR phosphorescence of Oxyphor G2 to detect therapy-induced exacerbation of hypoxia in the tumor microenvironment. This tissue oxygenation reporting system will also be used to assess vasoreactivity of tumor vessels to hypercapnea in an effort to develop noninvasive indicators of the functional reactivity and maturation state of tumor vessels and, hence, of their likely responsiveness to antiangiogenic agents. Aim 3 is to develop and test glucose analogs conjugated with NIR fluorophores to allow optical measurement of tumor glucose uptake as an indicator of enhanced glycolysis due to therapy-induced ischemia. These optical imaging studies will be validated and correlated with tumor histopathology and studies using other imaging modalities to examine the same or related tumor vascular and physiological parameters. These studies will identify optical approaches that report the tumor consequences of angiogenesis inhibition and advance both clinical implementation of optical imaging and rational development of antiangiogenic agents for cancer therapy.